The present invention relates generally to a method and apparatus for embossing a roll of material and more particularly relates to a method and apparatus for avoiding nesting in roll material.
Roll material, especially paper products such as paper towels, is typically provided with a pattern of embossments which adds bulk and texture to the roll material. Moreover, the embossments also affect the diameter of the roll of material depending upon the extent to which the embossments of adjacent layers of material are "nested" in one another.
Partial nesting of the embossments of adjacent layers of roll material can have the undesirable effect of causing a collapse or flattening of the non-nested embossments. Moreover, partial or substantial nesting of the embossments of adjacent layers of material reduces the "bulkiness" of the roll of material and also reduces the resiliency to squeezing of the roll of material.
For all of these reasons, it is desirable to minimize or to completely eliminate the nesting of embossments of adjacent layers of roll material especially in paper products such as roll paper towels.
As discussed in the background portion of U.S. Pat. No. 4,339,088 of Niedermeyer which issued on July 13, 1982, nesting can be completely eliminated if the repeat length of the embossment pattern in the machine direction is at least equal to the circumference of the finished roll. Conversely, if one desired to have complete nesting throughout the wound roll of material, the sketch repeat would likely have to be as long as the total footage in the wound roll, for example, about 200 lineal feet. As a result, most wound material having symmetrical embossments (i.e. on both sides of the roll material) have regions of relatively high nesting and relatively low nesting throughout the roll of material.
In U.S. Pat. No. 4,181,068 of Pollock which issued on Jan. 1, 1980 another embossing pattern for paper towels is disclosed wherein the pattern is provided in order to maintain a desired structure and absorption characteristic in the paper towels. The embossment pattern includes an arrangement wherein the repeat pattern is symmetrically oriented about a center line so as to form a helix of about five degrees relative to the machine direction.
Other embossment patterns for single-ply towels are disclosed in U.S. Pat. No. 3,337,388 of Wosaba which issued on Aug. 22, 1967 and in U.S. Pat. No. Re. 27,453 of Schutte et al. which issued on Aug. 1, 1972.
A different approach to solving the problems associated with wound material especially paper towels, involves the use of laminated paper structures including at least two plys of material each having an embossment pattern. The individual plys are then joined together at various locations. Examples of such laminated paper structures are disclosed in the following U.S. Pat. Nos. 3,414,459; 3,556,907; 3,672,950; 3,708,366; 3,738,905; 3,867,225; 3,867,872; 3,940,529; 3,961,119; 4,100,017; 4,307,141; 4,320,162; and 4,483,728.
The embossment arrangements for such laminated paper towels cannot be applied to single ply tissue and moreover is not particularly applicable to lightweight two ply paper products because of the additional expense and difficulty resulting from the need to combine the different plys together after the embossments have been provided in the individual plys. Moreover, the use of adhesive to join the plys together may interfere with the embossment pattern of the individual plys.
Accordingly, it is an object of the present invention to provide a repeating arrangement of embossments for a roll of material which embossments are configured so as to minimize nesting of adjacent layers of material in the roll.
Another object of the present invention is to provide a repeating arrangement of embossments having a repeat length in the machine direction which is less than the circumference of the finished roll and whereby the nesting of adjacent layers of material is minimized or eliminated.
Still another object of the present invention is to provide a method and apparatus for maximizing the bulkiness and roll diameter of roll material while maintaining resiliency in the roll material especially in paper towels by minimizing nesting in the roll material.
Yet still another object of the present invention is to provide a method and apparatus for minimizing the collapse of embossments in wound material especially paper towels by reason of partial nesting of the embossments of adjacent layers.
These and other objects of the present invention will become apparent to one skilled in the art upon reading the detailed description of the present invention in conjunction with the accompanying drawings.
According to the present invention, a roll of material is provided with a repeating arrangement of embossments which are configured so as to minimize nesting of the adjacent layers of material with the arrangement of embossments including a first array of projections which are generally regularly spaced from one another and a second array of projections (i.e. the first and second arrays are superimposed on one another in the same arrangement of embossments) with each projection of the second array extending longitudinally between two projections of the first array.
Furthermore, according to the present invention, a roll of material is provided with a repeating arrangement of embossments that is configured so as to minimize nesting of adjacent layers of material with the arrangement of embossments comprising a first array of generally conical projections arranged generally in a sinusoidal manner with a second array of projections superimposed on the first array of projections with each projection of the second array being substantially larger than each of the projections of the first array.